Vision functions for ascertaining the position of an object to be grasped and touch functions for ascertaining that the object to be grasped has been grasped are necessary in a robot hand for grasping objects. Vision and touch are complementary senses. Vision estimates the global condition, and touch ascertains the local condition. Complex sensors for imparting vision and touch functions to a robot hand are disclosed in the following patent documents.
In Patent Document 1 (JP-A 60-62496) there is disclosed a touch sensor combining sensing of contact, pressure, and proximity. The touch sensor disclosed therein has an optically transparent flexible plate-shaped part; a light-receiving part that is sensitive only to light from a front surface provided to a surface of the flexible plate-shaped part; and a light-emitting part for irradiating the flexible plate-shaped part from a rear surface of the light-receiving part, wherein reflected light that is emitted from the light-emitting part and reflected off an object of measurement is received by the light-receiving part; and the approach of the object of measurement to the plate-shaped part, the contact of the object of measurement with the plate-shaped part, and the pressure at the time of contact can be detected by the strength of the light received by the light-receiving part.
Disclosed in Patent Document 2 (JP-A 63-238502) is a proximity and touch sensor that is attached to a surface of a manipulator of a robot, whereby the approach of the manipulator to within, e.g., 20 cm of an obstacle or other object, and the contact of the manipulator with the object can be detected. In the proximity and touch sensor disclosed herein, electrodes are attached to both surfaces of a sheet-form pressure-sensitive conductive rubber; the capacitance to ground of the pressure-sensitive conductive rubber is measured, whereby proximity of the object is detected; and the electrical resistance of the pressure-sensitive conductive rubber is measured, whereby contact with the object is detected.
On the other hand, touch sensors that are capable of detecting the magnitude of a load acting on a detection surface, and the center position (position of the center of gravity) of the load acting on the detection surface have been proposed by one of the inventors of the present application. Specifically, in Patent Document 3 (JP-B 60-35602) there is proposed a method for detecting surface pressure data for detecting the magnitude of a load acting on a detection surface and the two-dimensional position of the center of gravity of the load. In Patent Document 4 (JP-B 06-58239) is proposed a sliding sensor that is capable of using a sheet-form touch sensor to detect sliding. In Patent Document 5 (WO2007/069412) there is proposed a sensor for detecting the center position of a two-dimensionally distributed load, where the sensor is composed of a flexible sheet.    [Patent Document 1] JP-A 60-62496    [Patent Document 2] JP-A 63-238502    [Patent Document 3] JP-B 60-35602    [Patent Document 4] JP-B 06-58239    [Patent Document 5] WO 2007/069412